Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.92	11.835%	$176.6098	$176.61	$176.60	$176.60
Purchase #2	$128.46	10.159%	$141.5103	$141.51	$141.50	$141.50
Purchase #3	$216.82	11.280%	$241.2773	$241.28	$241.30	$241.30
Purchase #4	$64.93	3.730%	$67.3519	$67.35	$67.35	$67.40
Purchase #5	$185.93	7.871%	$200.5646	$200.56	$200.55	$200.60
Purchase #6	$5.55	6.689%	$5.9212	$5.92	$5.90	$5.90
Purchase #7	$19.62	5.652%	$20.7289	$20.73	$20.75	$20.70
7 purchase totals =	$779.23		$853.9640	$853.96	$853.95	$854.00